Telephone plug shelf



Mar. 13, 1923. 1,%48,553

F. F. LUCJAS TELEPHONE PLUG SHELF Filed Apr. 24, 1920 'li'/ /n wnfal Franc/s Fla M 5 Patented Mar. 113, 1923.

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M4 553 FT FTC.

FRANCIS F. LUCAS, OF EAST ORANGE, 'NEW JERSEY, ASSIGNOR 'IO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YQRK, N. Y., A CORPORATION OF NEW YORK.

TELEIHQNE PLUG SHELF.

Application filed April 24, 1920.

T 0 aZZ whom it may concern Be it known that I, F nANcis F. Lucas, a citizen of the United States, residing at East Orange, in the county of Essex, State of ll ew Jersey, have invented certain new and useful Improvements in Telephone Plug Shelves, of which the following is a full, clear, conpise, and exact description.

This invention relates to plug shelves for telephone manual switchboards.

It has for an object to provide a shelf which will absorb the shocks which ensue in service to the plugs, plug shells and cords when these parts are restored to their nonoperative positions in the plug shelf.

Another object is to reduce the wear and abrasion of the switchboard cord.

In the sheet of drawings accompanying this specification, Fig. 1 shows an end view of a manual telephone switchboard; Fig. 2 is a cross-sectional view of the improved plug shelf; Fig. 3 a plan View ofthe shelf as constructed according to this invention; and Figs. 4 and 5 show a modification of the invention.

In Fig. 1, the switchboard l is represented in end view with the plug shelf 2 and one set of plugs 3 and 6 together with their respective cords 4 and 7 and their restoring cord weights 5 and 8. Plug 6 which, being situated nearest the board, is generally referred to as the answering plug, is shown inserted in the-board in its operative position. Plug 3, the calling plug, is in its n0n operative position, being held in position by its cord weight 5. The usual construction of the plug shelf 2 has heretofore quite generally been of a hard maple base faced with semi hard rubber. Upon returning plug from its operative position to its non-operative position the operator removes the plug from the jack in which it has been inserted and then allows th cord weight to restore the plug to the plug shelf. Before the plug finally comes to rest it goes through a series of motions due to the shifting of the center of gravity of the combination of the plug and cord and cord weight and also to the restraining influence which the plug shelf exerts on the cord as it passes through the cylindrical opening therein. fit first the plug assumes a horizontal. position, the tip pointing, for example, toward the left. The tip then strikes the base of the plug shelf from which it bounds and with a whip ac- Serial No. 376,257.

tion travels upward and over toward the right. The plug by this time acquires a relatively high velocity and continues in this state until it reaches a position somewhat similar to that shown in Fig. 2. At this point the travel is suddenly arrested and a rebound occurs, which is terminated when the plug is in a somewhat similar position to that shown in Fig. 2, leaning, however, toward the left. Finally'the plug reaches its seat and assumes a vertical position, such as that shown by plug 3 in Fig. 1. It will be clear that during these operations the plug tends to become wedged against the wall of the cylindrical opening in the plug shelf and from the motion imparted the tendency is to bend the plug over the rim of the plug shelf hole. That is, there is a resultant of forces which operates to break the plug and the plug shell much in the same manner as a small piece of wood might be broken over the knee. It will also be apparent thatt-he base of the plug will gouge the wall of the plug shelf opening. This produces a rough, splintery surface by which the cord is abraided. The bends imparted to the cord just below the base of theplug also tend to destroy the cord. This bending of the cord takes place at least four times during the restoration of the plug to its non-operative position. I

In accordance with the present invention, a plug shelf'is provided which willfabsorb the shocks of the plug and associated parts and thus decrease the breakage of these parts correspondingly. The surface of the plug shelf is, in accordance with the invention, made somewhat flexible and capable of moving slightly to prevent the tendency of the plugshell to wedge therein. To lessen the abrasion of the cord, a material of a softer and less fibrous and splintery nature than wood is provided.

Referring now to Figs. 2 and 3, which show more in detail the plug shelf as constructed in accordance with this invention, the semi-hard rubber facing 9 is secured by suitable means to a resilient material 10. It has been found that cork, which is a product from the stems and roots of woody plants which increase in diameter year by year and more particularly derivable from the outer layer of the bark of the evergreen species of oak, Quercus suker, is well suited for the resilient layer- Subproperties which make that in addition to its pressure resisting "PTOPBllZlBS, 1t also resists abrasion to a stances such as cork, whichhavethe power oflaltering their volume 1n-a veryimarked degree in consequence of change of pres- ,sure, furnish a means by which the shocks encountered in restoring plugs to their nonoperative position, may be absorbed. Such materials possessing an aggregation of minute air vessels having thin and very strong walls, whencompressed exhibit a' resistance of compression more like the reslst'anceof g BS than the resistance of an elastic material such as a spring. Sponge rubber, felt,-linoleum, andvthe like, have them desirable for use in this connection. Cork, however, appears to be 'superiorto other materials in marked degree and does not deteriorate rapidly. Other properties of cork which make its-use advantageous are its heat, comand moisture resisting qualities. 11- isattached to the bustion, The wooden strip under surface of the resilient material to which-the base strip 12 is affixed. Cylindrical openings 13 and 15 for the plug and cords respectively arefprovided together? with-the plug seat "1a.

As a modification of the above described with the thin wall of elastic material This l is considered to be desirable in cases where the plug 5 holes are necessarily situated in close proximity to one another, as is the case in some types o'f'telephone switchboards: The Cork inserts provide the neoessary flexibility andbecauseof the trough orlpslot construction, the baseof the plugs "donot -tend to-wedge in thesame manner asin 1the or'dina-r'y type of shelf. InFig;

4, a-plug shelf of the modified type is shown, -18 representing the i number plate aperture, which is" commonly placed at the rear or the plug."'The resilient layer is in this case made up of twov separate portions, the cylindrical vopening 13 being formed by the projections of the wooden base 11.

As a result of comparative tests which have been made using. the ordinary type of plug shelf and the one constructed in accordance with this invention, it was found that the: plug shelf embodying the resilient material showed no appreciable'wear after 85,000 operations, whereas the ordinary type I was badly worn after 7 0,000 operations.

From tests conducted utilizing a telephone plug equipped with a fibre plug shell, it

was apparent that, even under average ser:

vice conditions, the cushion type of plug shelfwill increase the life of both plu and shell approximately twelve times. aords which showed failure after 30,000 operations when used with the ordinary plug shelfwere still in good condition after-85 ,000 operations when the cushion plug shelfv was used. v l I \Vhile specific forms of construction are shown herein, it is apparent that this in vention may find application in other obvious modifications. i a

. -What is claimed isi 1. A laminated telephone plug shelf'having openings therein for the plugs, comprising an inner layer of cork.

' 2A telephone plug shelf comprising a rubber-faced resilient material with openings therethrough for the plugs and cords.

A telephone plug shelf comprising rubber-faced cork having openings therein t receive the plugs.

4:. A laminated telephone plug shelf comprising rubber, resilient material, and wood, and having openings'therethrough for the plugs I 5. A laminated 'telephone plug shelf com v posed of a base 'upon' whichthe'plugs rest, a layer ofresilient material,and animpact surface of semi-hard rubber; the base, resilient material' and impact surface having coincident openings therethrough.

In witness whereof I'he'reunto subscribe my name this 20th day of April A. D., 1920.

FRANCIS r. LUCAS. 

